In various practices it is desired to reinforce a hollow structural assembly, particularly structural members or sections which are subjected to edge or in-plane stresses which would tend to cause the structural member to buckle. Frequently holes are formed in structural members in order to weld internal reinforcements. Where, for example, the structural member is made of steel, a reinforcement is then welded to the structural member to prevent buckling. The holes would then be covered with cloth or plastic for appearance purposes.
It would be desirable if such hollow structural members could be reinforced by placing a reinforcement insert assembly into the hollow structure between the spaced walls in such a manner that would avoid the above problem. Typical applications for such practices could be in the automotive field, such as for reinforcing pillars. Other practices could be in the furniture field, such as for office furniture end shelving units where shelves are locked into vertical end walls or panels.
An object of this invention is to provide a reinforced structural assembly which meets the above needs.
A further object of this invention is to provide such a reinforced structural assembly which includes a stiffener capable of being readily placed into the assembly.
A still further object of this invention is to provide techniques for reinforcing a structural assembly.
A further object of this invention is to provide such practices which could be used for various applications, such as in the automotive field or in the furniture reinforcement field.
In accordance with one embodiment of this invention a stiffener is formed by interconnecting sets of laminates. Each laminate preferably comprises a carrier member and a cover member with an expandable polymer layer between the members. Preferably the polymer is heat curable. Each laminate contains notches so that the laminates can be interlocked to form a corrugated frame or lattice which may be inserted into a hollow structure. Upon curing and expansion of the polymer a structural foam results which is intimately bonded to the spaced side walls of the hollow structure. The hollow structure may, for example, be a pillar in an automobile or could be a hollow panel of a shelving unit.
In an alternative practice of the invention the stiffener could comprise an inverted U connected to an upstanding U with a common leg. An outward leg at one end of the laminate may extend upwardly beyond the remainder of the laminate so that the laminate could be placed in a lower pillar of a car at the junction of a hollow vertical section with a hollow horizontal section of the pillar for side impact or joint stiffening.
In a further alternative practice of the invention where the stiffener is a drop in insert for reinforcing a shelving unit, such as an office furniture end shelving unit. The laminate may be of straight linear construction and simply dropped into the unit so that the laminate extends generally from top to bottom of the hollow panel of the unit.
In a variation the stiffener could be bent such as to form a generally zig-zag shape.